1. Field of the Invention
The present invention related to a novel image forming material based on a material, the fluidity of which varies by the application thereon of an electric energy, and to a method for making an image by using the material.
2. Description of Related Art
In wet development processes for electrostatic photographs, almost all of the carrier liquids which have been hitherto proposed for wet development are organic solvents having high vapor pressures. Therefore, problems common to these processes are as follows: (1) Treatment of the carrier liquid vapor discharged is necessary at, for example, the time of fixing operation; (2) Some of the carrier liquids are inflammable; and (3) After the fixing treatment on such a substrate as paper, residual solvents in the substrate gradually evaporate and the copies generate the odors of the solvent. As a result, these processes cannot satisfactorily meet the recent requirements for environmental conservation.
As a means to avoid the above-mentioned problems, proposed are wet-process developers which are mainly composed of water or a water-soluble solvent that is safe and harmless to office environments and humans and developing methods using the same, such methods as wetting development, flight development, suction development, ink mist development and two-step development, which involve utilizing electroconductive developers.
Of these development methods proposed hitherto, one developing method where a photosensitive body and a developer liquid comes into direct contact with each other, makes it impossible to avoide the smearing of image and the adhesion of the liquid to the entire surface of paper because the developer wets the entire surface of the photosensitive body. A non-contact development system causes, in addition to the above-mentioned smear problem, an undesirable suction of a wet developer into the periphery of image, with the result that the fogging of the image and the bleeding at the fine lines of the image are not avoided. And, none of the development methods of prior art have provided satisfactory quality of image.
To solve these technical problems, one of the measures that have been proposed hitherto is the application of a molecular gel which causes a phase transition by such influencing factors as temperature, solvent composition, pH, ion concentration and electric field.
Details of molecular gels are described, for example, in "Materials having molecular functions and development of elements, Chapter 2, Elements" by the supervision of Takao Shimizu (published by NTS in 1994). Technical literatures other than this also provide the descriptions suggestive of the possibility that above-mentioned phenomenon may be utilized for a sensor, an actuator and a reactor, conversion elements for converting chemical energy into mechanical energy, artificial muscle, a display and a marking device.
For example, Japanese Patent Application Laid-Open (JP-A) Nos. 62-60,690 and 01-110,971 describe a direct marking process comprising the steps of directly supplying current to a gel by means of pattern-shaped, voltage applying electrodes to form an adhesive sol of ink and transferring the ink. Japanese Patent Application Laid-Open (JP-A) Nos. 01-136,761, 01-136,762 and 01-136,763 describe a direct marking process comprising the steps of sandwiching a gel between an absorbent membrane and a porous material held on an electroconductive substrate and supplying a current to the foregoing combination to discharge an ink, which will be transferred to paper through the porous material. None of these proposals has not been put into practice because of the problem of response speed to the volume change of the gel and of the stability at the time of repetitive use.